Command Line Provider

The command line provider parses command-line arguments into JSON configuration.

rule.For<AppSettings>().FromCommandLine("--app:")

How It Works

1. Scans arguments for entries matching the switch prefix (default --)
2. Parses key-value pairs from the matched arguments
3. Converts flat keys to nested JSON (same nesting rules as environment variables)

This provider is static — command-line arguments don't change during process lifetime.

Argument Formats

The parser supports several formats:

# Key=value (single argument)
--MaxRetries=10

# Key value (two arguments)
--MaxRetries 10

# Boolean flag (no value = "true")
--EnableLogging

# Nested keys with : or __
--Database:Host=localhost
--Database__Port=5432

Values that start with a switch prefix

In the two-argument --key value form, a value that itself begins with a switch prefix (e.g. --port -5) is parsed as a boolean flag (--port → true), not as the value -5. Use the = form for such values: --port=-5.

Prefix Filtering

Filter arguments by a prefix to avoid collisions:

// Only arguments starting with "--app:"
rule.For<AppSettings>().FromCommandLine("--app:")

dotnet run --app:MaxRetries=10 --app:Debug=true --other:Ignored=yes

Produces { "MaxRetries": 10, "Debug": true } for AppSettings. Arguments starting with --other: are ignored.

Custom Switch Prefixes ADV

By default, the parser looks for --. You can add other prefixes:

// Accept both - and -- as switch prefixes
rule.For<AppSettings>().FromCommandLine(["-", "--"])

dotnet run -MaxRetries=10 --Debug=true

When multiple prefixes match, the longest prefix wins.

Common Pattern

Command-line arguments as the highest-priority override:

rule => [
    rule.For<AppSettings>().FromFile("appsettings.json").Required(),
    rule.For<AppSettings>().FromEnvironment("APP_"),
    rule.For<AppSettings>().FromCommandLine("--app:"),  // Highest priority
]

Dynamic Options ADV

Use the factory overload for custom parsing:

rule.For<AppSettings>().FromCommandLine(accessor =>
    new CommandLineRuleOptions(
        Args: args,
        SwitchPrefixes: ["--", "-"],
        Prefix: "app"))